1. Field of the Invention
The present invention relates to an image processing apparatus that synthesizes acquired images to generate successive images, a control method therefor, and an image pickup apparatus.
2. Description of the Related Art
Conventionally, some image processing apparatuses in image pickup apparatuses or the like are configured to be capable of live view displays to successively display images acquired by an image pickup unit. In particular, there is known an image pickup apparatus capable of exposure simulation displays to display images based on an exposure setting value for shooting set in the image pickup apparatus.
Also, as described in Japanese Laid-Open Patent Publication (Kokai) No. 2008-079222, a plurality of images are acquired at regular intervals and held in a storage means, and in accordance with a set shutter speed, a predetermined number of images from the latest image being held are synthesized and displayed as a through image.
However, in the conventional apparatus capable of live view displays, when exposure simulation displays which display images with shooting exposure are produced, it is necessary to produce displays at a predetermined frame rate even at low brightness considering the following capability of images. At low brightness, however, exposure amount for a time period corresponding to the actual exposure value cannot be secured, and hence underexposed images may be displayed at exposure values different from the actual exposure values.
In apparatuses in which a plurality of images acquired at predetermined intervals are synthesized and displayed such as the one described in Japanese Laid-Open Patent Publication (Kokai) No. 2008-079222, for example, it is necessary to reserve storage space for storing images of 50 frames so as to acquire 10 frames per second and synthesize images of 5 seconds. Thus, when the number of frames to be synthesized increases, reserving memory capacity (storage space) for storing them becomes difficult, and there is a heavy computation load in image synthesis due to the need for synthesizing a number of images every time the composite image is updated.